为什么I一直小于0 表示弄一下午 都没成功 我是想插入一条数据 然后返回 i  若果i>0就注册成功 但是一直注册失败

int i = bll.Add(model, out msg);
if (i > 0)
{
//
Response.Redirect("/ShowMsg.aspx?msg=" + Server.UrlEncode(msg) + "&txt=" + Server.UrlEncode("首页") + "&url=/Default.aspx");
}

/// <summary>
/// 增加一条数据,部分类
/// </summary>
public int Add(BookShop.Model.Users model, out string msg)
{
//判断用户名是否已经被占用。
if (CheckUser(model.LoginId))//表示用户名已经被占用了
{
msg = "用户注册失败!!";
return -1;
}

msg = "注册成功";
return dal.Add(model);

}
/// <summary>
/// 根据用户名校验用户是否存在
/// </summary>
/// <param name="userName"></param>
/// <returns></returns>
public bool CheckUser(string userName)
{
Model.Users model = dal.GetModel(userName);
if (model != null)
{
return true;
}
else
{
return false;
}
}

/// <summary>
/// 根据用户名得到一个对象实体
/// </summary>
public BookShop.Model.Users GetModel(string userName)
{

StringBuilder strSql = new StringBuilder();
strSql.Append("select top 1 Id,LoginId,LoginPwd,Name,Address,Phone,Mail,UserStateId from Users ");
strSql.Append(" where LoginId=@LoginId ");
SqlParameter[] parameters = {
new SqlParameter("@LoginId", SqlDbType.NVarChar,50)};
parameters[0].Value = userName;

BookShop.Model.Users model = new BookShop.Model.Users();
DataSet ds = DbHelperSQL.Query(strSql.ToString(), parameters);
if (ds.Tables[0].Rows.Count >0)
{
if (ds.Tables[0].Rows[0]["Id"].ToString() != "")
{
model.Id = int.Parse(ds.Tables[0].Rows[0]["Id"].ToString());
}
model.LoginId = ds.Tables[0].Rows[0]["LoginId"].ToString();
model.LoginPwd = ds.Tables[0].Rows[0]["LoginPwd"].ToString();
model.Name = ds.Tables[0].Rows[0]["Name"].ToString();
model.Address = ds.Tables[0].Rows[0]["Address"].ToString();
model.Phone = ds.Tables[0].Rows[0]["Phone"].ToString();
model.Mail = ds.Tables[0].Rows[0]["Mail"].ToString();
return model;
}
else
{
return null;
}
}